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This module provides access to operating system functionality that is
standardized by the C Standard and the POSIX standard (a thinly disguised Unix
interface).

Do not import this module directly. Instead, import the module os,
which provides a portable version of this interface. On Unix, the os
module provides a superset of the posix interface. On non-Unix operating
systems the posix module is not available, but a subset is always
available through the os interface. Once os is imported, there is
no performance penalty in using it instead of posix. In addition,
os provides some additional functionality, such as automatically calling
putenv() when an entry in os.environ is changed.

Errors are reported as exceptions; the usual exceptions are given for type
errors, while errors reported by the system calls raise OSError.

Several operating systems (including AIX, HP-UX, Irix and Solaris) provide
support for files that are larger than 2 GB from a C programming model where
int and long are 32-bit values. This is typically accomplished
by defining the relevant size and offset types as 64-bit values. Such files are
sometimes referred to as large files.

Large file support is enabled in Python when the size of an off_t is
larger than a long and the longlong type is available and is
at least as large as an off_t. Python longs are then used to represent
file sizes, offsets and other values that can exceed the range of a Python int.
It may be necessary to configure and compile Python with certain compiler flags
to enable this mode. For example, it is enabled by default with recent versions
of Irix, but with Solaris 2.6 and 2.7 you need to do something like:

A dictionary representing the string environment at the time the interpreter
was started. For example, environ['HOME'] is the pathname of your home
directory, equivalent to getenv("HOME") in C.

Modifying this dictionary does not affect the string environment passed on by
execv(), popen() or system(); if you need to
change the environment, pass environ to execve() or add
variable assignments and export statements to the command string for
system() or popen().

Note

The os module provides an alternate implementation of environ which
updates the environment on modification. Note also that updating os.environ
will render this dictionary obsolete. Use of the os module version of
this is recommended over direct access to the posix module.